Tris(β-diketonato)iridium composed of iridium coordinated with β-diketone is known as a raw material compound (precursor) for use in chemical deposition methods such as a CVD method (chemical vapor deposition method) and an ALD method (atomic layer deposition method). For example, in Patent Literatures 1 and 2, there is described a raw material compound for chemical deposition for forming an iridium thin film composed of tris(5-methyl-2,4-hexanedionato)iridium or tris(2,4-octanedionato)iridium as an iridium complex.
Further, in recent years, there is investigated the application of a cyclometalated iridium complex, in which a multidentate ligand is coordinated annularly to iridium, to phosphorescent materials for an organic light-emitting element such as an organic electroluminescence (EL) element or an organic electrochemiluminescence (ECL) element (Patent Literature 3). Furthermore, tris(β-diketonato)iridium is also useful as a raw material (intermediate material) for manufacturing a phosphorescent material for an organic light-emitting element such as the cyclometalated iridium complex. For example, in Non Patent Literature 1, there is disclosed a method for manufacturing a phosphorescent material for an organic light-emitting element composed of cyclometalated iridium, by using tris(2,4-pentanedionato)iridium as a raw material and reacting the raw material with an aromatic heterocyclic bidentate ligand such as 2-phenylpyridine (ppy).
Here, as a method for manufacturing tris(β-diketonato)iridium, a process is known which uses an iridium salt such as iridium trichloride as a starting material, adds a β-diketone to be a ligand to the material, and adds potassium bicarbonate or the like to make the material alkaline and to react these (PTL 4).
The conventional synthesis method may synthesize directly above-described tris(5-methyl-2,4-hexanedionato)iridium, tris(2,4-octanedionato)iridium and tris(2,4-pentanedionato)iridium. However, the investigation by the present inventors confirms that the progress of a reaction is difficult in the conventional synthesis method in manufacturing of iridium complexes in which a wide range of β-diketones are coordinated.
For example, as for the above-described cyclometalated iridium complex as a phosphorescent material, it is necessary to investigate complexes coordinated with various ligands aiming at improvement in a luminous efficiency. In order to obtain a starting material for such a cyclometalated iridium complex, the inventors of the present application tried to synthesize iridium complexes in which a β-diketone was coordinated, the β-diketone having various structures containing an element such as fluorine excluding hydrogen/carbon, cyclic hydrocarbon, or the like, but did not recognize the progress of a synthesis reaction with the conventional method, and failed to obtain targeted tris(β-diketonato)iridium.